The present application relates to bearing assemblies and, more particularly, a hybrid bearing system that employs both a lubricating means and a self-lubricating means.
Bearings that allow rotation and misalignment have been and are used at the ends of actuators which move flight controls in aircraft applications. An example of flight controls includes, but is not limited to the following control surfaces in an aircraft: ailerons, rudders, elevators, elevons, ruddevons, flaperons, etc.
As the technology used in modern jet fighter aircraft and commercial aircraft has improved, the bearings used in these flight control actuator systems encounter different types of motions. In particular, the actuator systems encounter large types of motions and small constant or continuous dithering types of motions.
For example, most modern aircraft are designed with xe2x80x9cfly-by-wirexe2x80x9d or xe2x80x9cfly-by-lightxe2x80x9d active flight control systems. In these types of flight control systems high speed computers respond to minute changes in aircraft speed and attitude and the flight controls are continually actuated as the flight control systems continually xe2x80x9chuntsxe2x80x9d to find the proper position that the flight control should be at. The net effect of this operation is that the bearings associated with or connected to the ends of the flight control actuators are subject to very small and continuous dithering motions.
These motions are in addition to large motions that are a result of control input from the pilot (e.g. a large motions) which provides other areas of wear not associated with the small and continuous dithering motions mentioned above.
Many types and styles of bearings have been used in these flight control applications with marginal results normally resulting in premature removal of the bearing from aircraft service and increased maintenance costs and manpower which in turn increase the direct operating cost of the aircraft.
Two types of bearings systems have evolved, self-lubricating bearings and lubricating (e.g. grease) bearings or grease lubricated or dry film lubricated metal-to-metal bearings.
Self-lubricating bearings including fabric bearings and molded composite liner bearings that are designed to wear throughout their operational life or alternatively be used in an application where there is little movement or wear. Accordingly, the life of a fabric bearing or molded liner bearing depends on the application and the amount of wear that accumulates during use. In particular, and in aircraft applications where the bearing may encounter a large motions primarily due to larger flight control motions the bearing encounters greater wear that is a result of pilot control input.
Grease lubricated or dry film lubricated metal-to-metal bearings are characterized by having metal components which are grease lubricated or dry film lubricated. In a roller bearing, steel rolling elements are used which roll between two (2) other metal surfaces, for a metal-to-metal bearing two metal components slide relative to each other. In these bearings either grease or a dry film lubricant is used to lubricate the metallic surfaces. Theses bearing are not particularly well suited for very small dithering motions that are prevalent in an active xe2x80x9cfly-by-wirexe2x80x9d and xe2x80x9cfly-by-lightxe2x80x9d systems. The very small motions do not supply adequate oscillation of the bearing to distribute the grease and as a result the bearings can experience brinelling, fretting, seizure or bearing failure. In addition, these very small dithering type motions also cause the grease or dry film lubricant to migrate from the bearing metal-to-metal contact zone.
In addition, metal bearings are also commonly made of high hardness, non-corrosion resistant metals or metals that have been nitrided or malcomized which further reduces their corrosion resistance. Accordingly, corrosion coupled with inadequate lubrication a potential by-product of the very small dithering motions that does not adequately distribute the grease leads to brinelling, fretting, corrosion, seizure, or bearing failure.
Both the self-lubricating and grease lubricated bearings perform well with primarily one type of motion or in a particular type of application. The self-lubricating bearing works best with very small type dithering or vibrational motion while the grease lubricated bearing is designed to operate with large motions in which the grease is redistributed via the large motions (oscillations) in the bearing.
A hybrid bearing system that comprises a self-lubricating portion and grease lubricated portion disposed on the same surface, the system is adapted to accommodate at least two distinct wearing mechanisms generated by different types of motions.
A bearing system, comprising: a first member; a second member being configured to be rotatably received within the first member; a self lubricating machineable liner system disposed between the first member and the second member; a receiving area disposed on the self lubricating liner system and a portion of either the first or the second member; and a lubrication opening in fluid communication with the receiving area, the lubrication opening providing a means for disbursing a lubrication grease within the receiving area.
The above-described and other features of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.